IIRC to remove 3dr rear cards you need to take out some clips for the carpet. The large flat ones with two small holes unscrew. The smaller ones with a single hole need to be prised out. No need to take much care as the are pennies to replace.
the knocking could be a symptom of the miss fire rather than the cause so I have to agree about a poor connection in the main loom connector. Certainly worth a wiggle.
i did once upload pics of the ht leads on a dizzy block. Also do you have the plastic lead guides on the engine? The lead slots are numbered. As are the connectors on the dizzy cap cover.
I've been waiting until the National Meet was confirmed before printing any welcome letters. But they are on my list of stuff to do before Easter, regardless.